Test strips or biosensors are often used to measure the presence and/or concentrations of selected analytes in fluid test samples. For example, a variety of test strips are used to measure glucose concentrations in blood to monitor the blood sugar level of people with diabetes. These test strips include a reaction chamber into which a reagent composition has been deposited. Current trends in test strips require smaller test samples and faster analysis times. This provides a significant benefit to the patient, allowing the use of smaller blood samples that can be obtained from less sensitive areas of the body. Additionally, regarding measurement systems for blood glucose, for example, faster test times and more accurate results enable patients to better control their blood sugar level.
Electrochemical biosensors are well known and have been used to determine the concentration of various analytes from biological samples, particularly from blood. Examples of such electrochemical biosensors are described in U.S. Pat. Nos. 5,413,690; 5,762,770; 5,798,031; 6,129,823 and published application US2005/0013731, each of which is hereby incorporated by reference. For example, US2005/0013731 discloses an electrochemical biosensor having a covering layer US2005/0013731 discloses an electrochemical biosensor having a covering layer overlying a base substrate. The base substrate has an electrical pattern having electrodes and a reagent layer thereon. The base substrate and covering layer define a sample receiving chamber that draws fluid sample therein by capillary action, whereupon the fluid sample reacts with the reagent in the chamber. A voltage or potential is controlled or applied across the electrodes, and the current generated is measured at one or more times and is then correlated to analyte concentration. “Coulometric” and “potentiometric” techniques are also known in which charge or potential, respectively, instead of current is measured and correlated to analyte concentration.
Various techniques are known in the art to form the electrical patterns in electrochemical biosensors. For instance, screen printing is a wet material technique that generally allows reliable formation of electrode structures and patterns having a gap width or feature size of approximately 75 μm or greater.
Laser scribing usually employs a high power excimer laser, such as a krypton-fluoride excimer laser with an illumination wavelength of 248 nm, to etch or scribe individual lines in a conductive surface material and to provide insulating gaps between residual conductive material which forms electrodes and other desired components. The scribing is accomplished by moving the laser beam across the surface to be ablated, and such a technique can be undesirably time consuming if a complex electrical pattern is to be formed on the surface.
Broad field laser ablation is a technique that has recently been employed to manufacture electrochemical biosensors having incredibly accurate and highly defined electrical patterns with additional functionalities that have hitherto been unavailable. Examples of such electrochemical biosensors can be found in U.S. Pat. No. 7,073,246, U.S. Patent Publication Nos. 2005/0103624, 2006/0200981, and 2006/0200982, the disclosures of which are hereby incorporated by reference. Publication No. 2005/0103624 discloses a high degree of accuracy and definition with which electrical patterns can be formed with laser ablation. Similarly, U.S. Patent Publication No. 2005/0023137, which is also hereby incorporated herein by reference, discloses biosensors with incredibly small and complex electrical patterns that provide a large footprint on the base substrate for other components, such as a display and power supply, among others. Other known techniques involving lasers include laser induced forward transfer, or LIFT, such as is disclosed in U.S. Pat. Nos. 6,177,151 and 4,752,455, and PCT/US/2006/035312, each of which is hereby incorporated by reference herein.
It would be desirable to further improve the electrical patterns and method of making the same in electrochemical biosensors.